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Strict Comparison Operator Doesn't Infer Singleton Types Correctly #6940

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Strict Comparison Operator Doesn't Infer Singleton Types Correctly#6940
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@vlad-shatskyi
Volodymyr Shatskyi (vlad-shatskyi)
opened on Feb 6, 2016

Having a singleton type type A = "a" | "b", a variable const a: A = "a", and an expression a === "c", the compiler should infer the type of "c" as A and make the expression unsound.

Currently (1.8.0 and 1.9.0-dev.20160206) it compiles, which makes usage of singleton types instead of enums less type safe.

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  1. Ryan Cavanaugh (RyanCavanaugh)
    added
    SuggestionAn idea for TypeScript
    In DiscussionNot yet reached consensus
    on Feb 6, 2016

  2. RyanCavanaugh commented on Feb 6, 2016

    @RyanCavanaugh
    Ryan Cavanaugh (RyanCavanaugh)
    on Feb 6, 2016
    Member

    This is a good idea

  3. weswigham commented on Feb 8, 2016

    @weswigham
    Wesley Wigham (weswigham)
    on Feb 8, 2016
    Member

    #6196 should fix this, right?

  4. vlad-shatskyi commented on Feb 8, 2016

    @vlad-shatskyi
    Volodymyr Shatskyi (vlad-shatskyi)
    on Feb 8, 2016
    Author

    Yes, Wesley Wigham (@weswigham). Closing this issue.

  5. Volodymyr Shatskyi (vlad-shatskyi)
    closed this as completedon Feb 8, 2016
  6. Ryan Cavanaugh (RyanCavanaugh)
    added
    DuplicateAn existing issue was already created
    and removed
    In DiscussionNot yet reached consensus
    SuggestionAn idea for TypeScript
    on Feb 8, 2016
  7. microsoft
    locked and limited conversation to collaborators on Jun 19, 2018
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